In 1989 I wrote the following (Rushall & Pyke, 1990, Training for sports and fitness):

A further suggestion, for which there is no scientific evidence, is to live at altitude but train at sea level. With that regimen, the body will still be able to maintain training volumes and intensities, and also experience the overcompensatory aerobic adaptations of altitude. This situation would present the best characteristics of both sea level training (big volumes and high intensities) and altitude living (exaggerated aerobic adaptations). In theory, under these conditions the level of endurance performance should increase. (p. 138)

So, I have to take some blame for this, although I only ever envisaged hypoxic and hypobaric recovery conditions using natural environments, the so called live-high -- train-low protocol.

However, now these tents, which are very popular here in the USA, produce hypoxic and normobaric conditions in a totally contrived environment. That worries me somewhat.

The evidence for the use of tents is quite persuasive in volume, but is following a path of less than adequate scientific structure. The typical research inadequacies of the initial altitude literature, whose implications were eventually disproved for performance levels at sea level, appear to have been resurrected in live-high -- train-low and nitrogen-tent studies.

Only in the last year have I located a study that showed no improvement with the tent under a special circumstance. I still have not determined the role or differences between hypobaric and normobaric conditions. I do not know of any study that has assessed this. It is the central factor that differentiates live-high -- train-low and nitrogen-tent experiences, so it should be worthy of investigation.

In my opinion, these training protocols are currently at fad status. Why would Ed Moses, a sprinter, use the tent when its benefits are supposed to be aerobic, especially blood factors? Is it supposed to give him greater training volumes at race-pace intensity (something not yet shown)? I am not sure I can see the wisdom in using it in his case.

NEVERTHELESS, there is a form of experimentation that is going on. Athletes use these tents for only some part of the year and for only part of the day, but are their performances that much worse than when not used? There are so many factors involved in performance, very influential ones being the motivation for performing and the opportunity for restorative recovery, that to single out one item that is physiologically based, while ignoring all others, is very questionable. It still is new knowledge, but is rarely considered, but the fact that physiological indices, such as the state of the blood, have very little to do with short term event performances, such as most swimming events, that it becomes a real stretch of the imagination to see tents producing enough effect to actually cause performances to change. I suspect the placebo effect is very much involved with the majority of the current positive research findings involving at least these tents. Also, they might "force" better quality rest which facilitates recovery from fatigue.

I know of no mechanism that selects a stress (e.g., hypoxia), starts to adapt to it, and maintains accumulated adaptation, when the stress is removed (i.e., when outside of the tents) for the greater proportion of each day. The body normally would undergo readaptation. It has been shown that the dominant stress, which in this case would be normobaric normoxia, would dominate any adaptation. Have the "altitude physiologists" discovered a "selective adaptive memory" that supports their eternal attempt to prove some value in altitude training?